Chemical process



May 16, 1950 b s 7 2,507,527

CHEMICAL PROCESS 7 Original Filed July 13, 1945 Mn NA PHTH ETHYLNAPHTHALENE.

CAUSTIC EXTRACTOQ RESIDUE'.

uvsggrou HYDROGEN osnmnzm'rou mm HEATER IN VEN TOR.

IPOBERT Jomvsam Patented May 16, 1950 UN ED TATES OFF ICE CHEMICALPROCESS ration of Delaware Original application July 13, 1945, SerialNo. 604,806. Divided and this application October 5, 1946, Serial No.701,407.

4 Claims.

This invention relates "to the manufacture of derivatives of ethylnaphthalene and more particularly is directed to processes forconverting ethyl naphthalene to methyl naphthyl carbinol.

This application is a division of my copending application604;80.6,'filed July 13, 19%, now Patent .Number 2,468,759.

The invention has for its objects to provide new and improved methods ofmaking derivatives vof ethyl naphthalene; to provide new and improvedmethods of convertingethyl naphthalene to methyl naphthyl carbinol; toavoid the disadvantages of the prior art and to obtain advantages aswill appear hereinafter. These objects will become apparent as thedescription proceeds.

The foregoing objectsare accomplished in the present invention by actingupon ethyl naphthalene with oxygen in'the presence of an oxidationcatalyst at a reactive'temperature below that at which substantialdehydration of methyl naphthyl carbinol occurs. Under these conditionsthe ethyl naphthalene is oxidized to a mixture of methyl naphthylarbinol and methyl .naphthyl ketone. This mixture may be utilized assuch or further treated to recover the separate elements or to convertthem to other desirable derivatives.

It is possible to obtain vinyl naphthalene by dehydrogenating ethylnaphthalene. .A simple as this process appears, however, it iscomplicated by the difficulty of recovering the vinyl naphthalene fromthe reaction mixture. The vinyl naphthalene so readily .polymerizes thatit is difficult to separate vinyl naphthalene from the unchanged ethylnaphthalene by distillation. It is an object of the invention thereforetoprovide "methods for converting ethyl naphthalene to vinyl naphthalenewhich are free of these disadvantages.

This particular object is accomplished in the present invention byoxidizing ethyl naphthalene to a mixture of methyl naphthyl carbinol andmethyl naphthyl ketone, hydrogenating the "methyl naphthyl ketone tomethyl naphthyl carbinol and dehydrating the met iyl naphthyl carbinolto vinyl naphthalene. The unreacted ethyl naphthalene may be distilledoff either be "fore or after hydrogenation, or both before and afterhydrogenation, so that it is possible by the combination of steps setforth easily and effectively to obtain ahigh yield of vinyl naphthaleneuncontaminated with ethyl naphthalene.

In carrying out'the methods of the invention the ethyl naphthalene isfirst oxidized to a mixture of methyl naphthyl 'carbinol and methyl InCanada July 8,

naphthyl ketone by acting .upon it with air or other suitableoxygemcontaining .gas in the presence of an oxidation catalyst.The'temperature during the oxidation is carefully regulated so that itdoes not exceed that temperature at which substantialdehydration ofmethyl naphthyl carbincl would take place. The temperature may suitablyrange up to'about 175 C. but above this temperature dehydration of.methyl nap'hthyl carbinol proceeds'too rapidly. Any lower reactivetemperature may be used Which ordinarily Will not be less than about C.The pressure is not critical but may vary from atmospheric or less to 4%p. s. i. or more. Thepressure ordinari- 1y will be moderate (-less than100p. s. i.) in 'view of the high boiling point of ethyl naphthalene.

Manganous naphthenate has been found to be unusually efiective inpromoting the oxidation of ethyl naphthalene. With this catalyst,conversions in the order of 20-30% are obtainable at 100-125" C. Watermay be present without affecting the conversion other than to 'slow downthe reaction rate. Temperatures higher than C., while permissible, werenot observed to give increased overall conversion.

Other materials observed to promote oxidation include cobalt stearate,cobalt naphthenate, cupric acetate, manganous acetate, manganouscarbonate, chromicnaphthenate and a mixture of manganous acetate andbenzaldehyde.

The crude product of the oxidation consists predominantly of unreactedethyl naphthalene and the balance consists mainly of a substantiallyequal mixture of :methyl naphthyl carbinol and methyl naphthyl ketonealong with small amounts of unidentified acidic and neutral by-products.It may be treated in various ways to recover the oxygenated ethylnaphthalene.

A suitable method of refining the crude oxidation product is bydistillation. If desired, the crude product mayfirst be extracted withcaustic solution to remove the acidic constituents. The unconvertedethyl naphthalene issufliciently low boiling that it may be easilyseparated from the oxygenated compounds. The distillation should beeifected under a pressure suificiently below atnfo spheric to keep thetemperature below that at which substantial dehydration of methyl'naphthyl carbinol would take place. At a suitable pressure, say 3-5 mm.Hg, the unconverted ethyl naphthalene may be taken oil as a first cut(120 to C. at 10 mm. Hg) and recycled to the oxidation, the mixture ofmethyl naphthyl carbinol and methyl naphthyl lcetone taken oil as asecond cut (145 to C. at '10 mm. Hg) and the neutral by-products asbottoms or alternatively the mixture of methyl naphthyl carbinol andmethyl naphthyl ketone may be taken off in the bottoms along with theneutral by-products. These mixtures of alcohols and ketones may beutilized as such or passed on for further processing. Thus the mixturemay be subjected to hydrogenation according to a preferred process ofthe invention in order to convert the ketone to an alcohol, or themixture may be otherwise treated to separate the alcohol and ketone, forexample by esterifying the alcohol and then distilling the ketone awayfrom the ester. lhese and other methods may be utilized for recoveringthe various products of the oxidation.

The following table illustrates a typical product distribution TABLE IOxidation of ethyl naphthalene at 100 and 125 with 1.5% of manganesenaphthenate 1 Mixed isomers-about 50% alpha and 50% beta.

2 The oxidation products were extracted with caustic to remove acidicby-products. The acids were liberated from caustic with acid, taken upin ether, and weighed after solvent removal. The neutral products weredistilled at 3-5 mm. to efiect separation into unreacted ethylnaphthalene, methyl naphthyl ketone-l-mcthyl naphthyl carbinol, and aresidue of distillation containing the higher boiling neutral productsof oxidation. The products were distilled at low pressure in a columnwith low pressure drop (Vigreux type) to avoid dehydration of methylnaphthyl carbinol.

In the accompanying flow sheet there is illustrated diagrammaticallyapparatus suitable for carrying out the oxidation and separationsdescribed above. Ethyl naphthalene and manganous naphthenate areintroduced into the receiver I and the solution of manganous naphthenatein ethyl naphthalene is passed through line 2 into a converter 3provided with a suitable jacket 5 through which a heat transfer mediummay be circulated to maintain the desired temperature in the converter.Simultaneously air is forced into the bottom of the converter bycompressor 5, bubbled up through the ethyl naphthalene solution andvented through vent 6. The oxidation product is withdrawn through line 1into a caustic extractor 8 where it is washed thoroughly with sodiumhydroxide solution. This solution, containing the acidic by-products, iswithdrawn through line 9 and the washed product is passed through lineH] to filter I l where the manganous hydroxide and oxide precipitated inthe solution are filtered off. The filtrate passes through line [2 intoa distillation column IS. The first fraction is taken off as overhead,condensed in a suitable condenser M and collected in a receiver [5whence it is pumped back to the receiver I through line Hi. The secondfraction is taken 01f as bottoms and further fractionated in column Amixture of methyl naphthyl carbinol and methyl naphthyl ketone distillsover and a residue of tarry materials is left as bottoms. The distillateis condensed in condenser l8 and collected in receiver I9 for use assuch or for further processing.

In accordance with a preferred operation of the invention the mixture ofmethyl naphthyl carbinol and methyl naphthyl ketone obtained in theoxidation of ethyl naphthalene, either crude or refined as describedabove, is hydrogenated to yield a product which is predominantly methylnaphthyl carbinol by acting upon the mixture witlrhydrogen in thepresence of a hydrogenation catalyst at a reactive temperature belowthat at which substantial dehydration of the methyl naphthyl carbinoltakes place. The temperature may suitably range up to about 175 C. butabove this temperature dehydration of methyl naphthyl carbinol proceedstoo rapidly. Any lower reactive temperature may be used which ordinarilywill not be less than about 100 C.

A copper chromite catalyst has been found suitably effective inhydrogenating methyl naphthyl ketone. With this catalyst conversion inthe order of 94% of theory was obtained at 100 to 125 C.

In this operation the methyl naphthyl ketone is reduced to methylnaphthyl carbinol and small amounts of by-products are either formedduring the hydrogenation or carried through from the original crude. Thehydrogenated product may therefore be treated to recover the desiredproduct methyl naphthyl carbinol in a relatively pure form. This may beeffected by distilling the crude hydration product at a pressuresufiiciently below atmospheric to give a temperature below that at whichsubstantial dehydration of the methyl naphthyl carbinol takes place. Ata suitable pressure, say 4-10 mm. Hg, a low boiling fraction (-l30 C. at4 mm. Hg) may be taken ofi as the first cut and either discarded orreturned to the oxidation and the methyl naphthyl carbinol may be takenoil as the second cut (130-140" C. at 4 mm. Hg) and utilized as such orsubjected to further processing such as crystallization. The residue maybe discarded.

The following table illustrated a typical product distribution:

TABLE II Hydrogenation of methyl naphthyl ketone in the ketone-carbinolmixture to methyl naphthyl carbinol Grams of charge grams 639 2,200Grams of catalyst .do 50 Temperature C 115-420 Product analysis(distillation at 2-4 Forerunnings B. P. 85-130/4 mm 25 100 MethylNaphthyl arbinol B. P.

-l 0/4 mm 517 1,745 Residue slight slight In the accompanying flow sheetthere is illustrated diagrammatically apparatus suitable for carryingout the hydrogenation as described above. The mixture of methyl naphthylketone and methyl naphthyl carbinol from receiver i9 is passed throughline 20 upwardly through a con verter 2|. The converter 2i is packedwith a suitable hydrogenation catalyst, such as copper chromite, incatalytic tubes 22 which are surrounded by a jacket 23 for circulating aheat transfer fluid around the tubes 22 in order to maintain thecatalyst at the desired temperature. Hydrogen is introduced at 24,bubbled u through the converter 2! and vented at 25. The hydrogenatedproduct passes out of the converter through line 26 into thedistillation column 21. The light ends are condensed by a condenser 28and collected in receiver 29 whence they are returned through lines 30and 16 to receiverl.

75 The bottoms are passed through line 3| into a second column 32 wheremethyl naphthyl carb'inolis taken off as overhead and any residue asbottoms. The methyl naphthyl carbinol fraction is condensed in acondenser 33 and collected in a receiver '34 whence it may be withdrawn{or useas 'such'or for further processing.

In accordance with a preferred embodiment of the invention the methylnaphthyl carbinol recovered from the hydrogenation operation "isconverted to vinyl naphthalene by passing methyl naphthyl carbinol incontact with a dehydration catalyst which suitably is a surfacecatalystsuch as Activated alumina. Under suitable conditions oftemperature and pressure dehydration of the methyl naphthyl carbinol isefiected. At a tem- '15 perature of 140 0. methyl naphthyl carbinol is"stable for .a 'long'period; at 160 C. it is dehydrated in two hours andat 250 'C. it is dehydrated in hours. At higher temperatures and in thepresence of a suitable dehydration catalyst, methyl naphthyl carbinolmay be substantially completely dehydrated. Unless care is utilized,however, the vinyl naphthaleneformed in the dehydration is substantiallypolymerize ciently pure for technical purposes.

pressure of the methyl naphthyl carbinol vapors over the surfacecatalyst by diluting them with asuitableinert diluent gas such ascarbon'dioxide.

A product may be thus obtained which is sulfi- Where a more highlyrefined product is desired however or where the dehydration throughinactivation of catalyst leaves a substantial proportion of the methylnaphthyl carbinol uncl-ianged, the product may be purified bydistillation at a pressure sufiiciently below atmospheric to give atemperature below that at which substantial polymerization of vinylnaphthalene takes place. Unlike the case of ethyl naphthalene and vinylnaphthalene the boiling points or methyl naphthyl carbinol vinylnaphthalene are suiiiciently TABLE III Dehydration of methyl naphthylcarbinol to vinyl naphthalene over Activated alumina with and withoutCO2 as diluent 1 Liquid space velocity is equivalent to ml. of methylnaphthyl carbinol per ml.

of catalyst per h 1 Total gas space velocity is equivalent to 1111. ofgaseous methyl napthyl carbinol +0 01 at standard conditions per ml. ofcatalyst per hour. 3 Fresh catalyst as indicated in the table wascharged to the unit before startmg the run whereas in other runs thecatalyst from preceding run was used.

In order to avoid polymerization of vinyl naphthalene in th dehydration,it is necessary to eiiect a suitable balance between the temperature ofthe dehydration reaction and the time of exposure. If the temperature istoo high or if the time is too low, undesirable polymerization of vinylnaphthalene takes place. I have found that temperatures between about300 and 350 C. with a surface catalyst, such as Activated alumina, thespace-velocity may easily be so regulated as to obtain high conversionof methyl naphthyl carbinol to vinyl naphthalene with substantially nopolymerization. Those skilled in the art will readily be able, in viewof the illustrative data given, to select space-velocities which areoptimum to minimize polymerization. Ordinarily a liquid space-velocityof about 1 or 2 is satisiactory. It is possible also to obtain vinylnaphthalene by distilling methyl naphthyl carbinol over caustic soda ina suitable high vacuum, low pressure drop still. Distillation withoutpolymerization of vinyl naphthalene, however, is diflioult and it ispreferred, therefore, to effect dehydration over a surface catalyst.

The dehydration is most suitably effected at atmospheric pressurealthough higher or lower pressures, while not economical, neverthelessmay be used. It is desirable to reduce the partial In the accompanyingflow sheet, there is illustrated diagrammatically apparatus suitable foreffecting dehydration of ethyl naphthyl carbinol to vinyl naphthalene.Methyl naphthyl carbinol from receiver 34 is passed through a line 35into a heater 36 where it is heated as required to vaporize it. Thevapors pass through line 31 where they are diluted with carbon dioxideat 38 into the dehydration converter 39. The converter 39 is packed withActivated alumina as catalyst in the converter tubes 9 which aresurrounded by the jacket ll by means of which a heat transfer medium maybe circulated in contact with the tubes lil. The vapors pass throughline Q2 into the condenser 3 and the condensate is collected in thereceiver st for use as such or for further processing, The carbondioxide is vented at 45. The carbon dioxide may be preheated if desiredto supply all or part of the heat necessary to vaporize the carbinol. Ifthe distillation is conducted under optimum conditions which have beendescribed above, high yield of vinyl naphthalene free of polymers andmethyl naphthyl carbinol may be obtained. Should substantial quantitiesof these products be formed, however, they may be separated bydistillation. Thus the vinyl naphthalene from receiver 44 may be passedthrough line 46 into distillation column 41 from which vinylnaphthalene-may be recovered as overhead, condensed in condenser 48 andcollected in receiver 49 and methyl naphthyl carbinol may be taken on asbottoms and returned through line 50 to the hydrogenation conversion.

While I have described my invention with reference to particularembodiment thereof, it will be understood that variation may be madetherein without departing from the spirit and scope of the invention.

I claim:

1. The process which comprises acting upon ethyl naphthalene in theliquid state with oxygen in the presence of an oxidation catalyst at areactive temperature below that at which substantial dehydration ofmethyl naphthyl carbinol occurs thereby to obtain a mixture of methylnaphthyl carbinol and methyl naphthyl ketone and acting upon saidmixture in the liquid state with hydrogen in the presence of a cupricchromite hydrogenation catalyst at a reactive temperature between about100 and 175 C.

2. The process which comprises acting upon a mixture of methyl naphthylcarbinol and methyl naphthyl ketone in the liquid state with hydrogen inthe presence of a cupric chromite hydrogenation catalyst at a reactivetemperature between about 100 and 175 C.

3. The process which comprises acting upon a mixture of methyl naphthylcarbinol and methyl naphthyl ketone with hydrogen in the presence ofcupric chromite at a temperature of about 100 to 125 C. thereby toreduce the methyl naphthyl ketone to methyl naphthyl carbinol.

4. The process which comprises acting upon ethyl naphthalene in theliquid state with oxygen in the presence of manganous naphthenate at atemperature between about 100-125 0., thereby 8 to obtain a mixturecontaining methyl naphthyl carbinol, methyl naphthyl ketone andunreacted ethyl naphthalene, subjecting said mixture to fractionation ata pressure below atmospheric such that the temperature is below that atwhich substantial dehydration of methyl naphthyl carbinol takes place,returning the ethyl naphthalene fraction to the process, acting upon themixture of methyl naphthyl carbinol and methyl naphthyl ketone withhydrogen in the presence of cupric chromite at a temperature of about100 to 125 C. thereby to reduce the methyl naphthyl ketone to methylnaphthyl carbinol, subjecting the hydrogenation product to distillationat a pressure below atmospheric such that the temperature is below thatat which substantial dehydration oi. methyl naphthyl carbinol takesplace, returning the low boiling fraction to the oxidation.

ROBERT JOHNSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,813,606 Binapfi July 7, 19312,079,414 Lazier May 4, 1937 2,091,800 Adkins et a1. Aug. 31, 19372,137,407 Lazier Nov. 22, 1938 2,376,674 Emerson et a1. May 22, 1945OTHER REFERENCES Palfray, Bull. Soc. Chim., 7,401-6 (1940). ChemicalAbstracts, vol. 36, col. 2837-2839 (1942) Petrov et a1., ChemicalAbstracts, vol. 22, col. 2073 (1928).

1. THE PROCESS WHICH COMPRISES ACTING UPON ETHYL NAPHTHALENE IN THELIQUID STATE WITH OXYGEN IN THE PRESENCE OF AN OXIDATION CATALYST AT AREACTIVE TEMPERATURE BELOW THAT AT WHICH SUBSTANTIAL DEHYDRATION OFMETHYL NAPHTHAL CARBINOL OCCURS THEREBY TO OBTAIN A MIXTURE OF METHYL